Seven years ago Kate Mosse’s personal finances were examined by a newspaper advice column that struggled to suppress its alarm at her lack of savings. “Kate should start aggressively to build up a decent pension pot,” the expert chided.

Mosse need not have worried. It has been raining money since her novel Labyrinth was featured on Richard & Judy’s book club, and her success was sealed when the book was named “best read of the year” at the British Book Awards last week.

The way in which her holy grail theme, striking a chord with a public entranced by Dan Brown’s novel The Da Vinci Code, became a pot of gold is etched on The Sunday Times bestseller list of paperback fiction. The book is in its seventh consecutive week in the top spot, a record surpassed only by Brown’s blockbuster and Mark Haddon’s The Curious Incident of the Dog in the Night-Time.

“I still feel like I have to pinch myself,” the 44-year-old author said recently. Since Labyrinth was published last year it has notched up 418,000 sales and has been translated into 32 languages.

Mosse has seemingly erupted on the scene yet carries the baggage of someone who already has it all, prompting some envy. Not only is she blonde, vivacious and has a name often confused with a famous model, but she also worked in publishing and co-founded the £30,000 Orange literary prize for women’s fiction. In 2000 she was named European woman of achievement for contribution to the arts.

Damn it, Mosse has even invaded broadcasting, presenting the literary programmes Open Book on Radio 4 and BBC4’s Readers and Writers Roadshow. “She’s bubbly, charming and is a real enthusiast for books,” says one guest. “She told me she re-reads all of Agatha Christie every year and is a great fan of Conan Doyle.”

Then there is Mosse’s picturesque second home beside the walled city of Carcassone in southwest France where she lives for four months of the year with her husband Greg, daughter Martha, 16, and son Felix, 13. A large house in Bognor Regis, West Sussex, serves as their British base.

Some people look askance at the fact that her husband changed his name to Mosse by deed poll. Mosse’s explanation is that when Greg’s parents divorced, his mother reverted to her maiden name and he saw less of his father. “Greg wanted a visible connection to me and our children,” she said. “But there was never any question that it would be anything other than Mosse.” The Da Vinci Code appeared in the bookshops just as Mosse finished her first draft and before she began seriously editing Labyrinth. “It’s a terrific read,” she said. “Both have the idea of the grail at the centre but Dan Brown’s is the traditional holy grail and mine is not.” So there.

Labyrinth has been described as the thinking woman’s summer reading, or “chick lit with A-levels”, highly readable but sometimes frustrating. Set in the 13th century and the present, it concerns the safety of a set of books dating back to ancient Egypt and guarded by the Cathars, a persecuted sect in the French Pyrenees.

There are two heroines, a 13-year-old girl from Carcassone and a contemporary British woman who inveigles her way on to a local archeological dig. Unusually, all the main roles are taken by women.

It reflects Mosse’s frustration as a left-wing feminist at the lack of adventure writing for women. “Almost all the stories I’ve read are very much hero-driven, with women as the handmaidens,” she said.

“I was keen to see if I could write an adventure story where the women get to have lovely frocks, sex and swords and don’t wait to be rescued.”

Her interest in swashbuckling led her to take sword-fighting lessons — “just so I had an idea of what it felt like to hold a medieval fighting sword in my hand” — and build up a collection of weapons, some bought at an antique shop in Carcassone (close to the Blanche de Castille patisserie, which stocks her favourite croissants, pain au chocolat, tartes and madeleines).